[PATCH net v2 1/2] net: macb: zero the link settings taprio reads back

[Aleksei Sviridkin <f@lex.la>]

macb_taprio_setup_replace() calls phylink_ethtool_ksettings_get() with
an uninitialised kset, and kset is not only an out-parameter. On a
fixed link, or an in-band link with no PHY, phylink writes speed and
duplex only if kset->base.rate_matching already reads RATE_MATCH_NONE,
a field it never writes itself; in PHY mode before the PHY is attached
it writes port and supported and nothing more. Either way the speed
read back afterwards can be stack garbage. The ethtool core zeroes the
structure on every path into the op, which is why its callers never
see this; taprio is the only in-kernel caller passing its own variable.

Fixes: 89934dbf169e ("net: macb: Add TAPRIO traffic scheduling support")
Assisted-by: LLM
Signed-off-by: Aleksei Sviridkin <f@lex.la>
---
v2: message rewritten, declaration in reverse xmas tree order (Théo
    Lebrun).

 drivers/net/ethernet/cadence/macb_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 76ee4f506033..61838084989a 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -4295,9 +4295,9 @@ static int macb_taprio_setup_replace(struct net_device *netdev,
 	u64 total_on_time = 0, start_time_sec = 0, start_time = conf->base_time;
 	u32 configured_queues = 0, speed = 0, start_time_nsec;
 	struct macb_queue_enst_config *enst_queue;
-	struct tc_taprio_sched_entry *entry;
+	struct ethtool_link_ksettings kset = {};
 	struct macb *bp = netdev_priv(netdev);
-	struct ethtool_link_ksettings kset;
+	struct tc_taprio_sched_entry *entry;
 	struct macb_queue *queue;
 	u32 queue_mask;
 	u8 queue_id;
-- 
2.53.0